UNIVERSITY  OF   CALIFOBHIA   PUBLICATIONS 

COLLEGE  OF  AGRICULTURE 

AGRICULTURAL  EXPERIMENT  STATION 
BERKELEY,  CALIFORNIA 


A   SPOTTING  OF   CITRUS   FRUITS   DUE 

TO  THE  ACTION  OF  OIL  LIBERATED 

FROM  THE  RIND 


BY 
HOWARD  S.  FAWCETT 


BULLETIN  No.  266 

Berkeley,  Cal.,  February,  1916 


UNIVERSITY  OF  CALIFORNIA  PRESS 

BERKELEY 

1916 


Benjamin  Ide  Wheeler,  President  of  the  University. 
EXPEEIMENT  STATION  STAFF 

HEADS   OP   DIVISIONS 

Thomas  Forsyth  Hunt,  Director. 
Edward  J.  Wickson,  Horticulture  (Emeritus). 

Herbert  J.  Webber,  Director  Citrus  Experiment  Station;  Plant  Breeding 
Hubert  E.  Van  Norman,  Vice-Director;  Dairy  Management. 
William  A.  Setchell,  Botany. 
Myer  E.  Jaffa,  Nutrition. 

Eobert  H.  Loughridge,  Soil  Chemistry  and  Physics  (Emeritus). 
Charles  W.  Woodworth,  Entomology. 
Ralph  E.  Smith,  Plant  Pathology. 
J.  Eliot  Coit,  Citriculture. 
John  W.  Gilmore,  Agronomy. 
Charles  F.  Shaw,  Soil  Technology. 

John  W.  Gregg,  Landscape  Gardening  and  Floriculture. 
Frederic  T.  Bioletti,  Viticulture  and  Enology. 
Warren  T.  Clarke,  Agricultural  Extension. 
John  S.  Burd,  Agricultural  Chemistry. 
Charles  B.  Lipman,  Soil  Chemistry  and  Bacteriology. 
Clarence  M.  Haring,  Veterinary  Science  and  Bacteriology. 
Ernest  B.  Babcock,  Genetics. 
Gordon  H.  True,  Animal  Husbandry. 
James  T.  Barrett,  Plant  Pathology. 
Fritz  W.  Woll,  Animal  Nutrition. 
A.  V.  Stubenrauch,  Pomology. 
Walter  Mulford,  Forestry. 
W.  P.  Kelley,  Agricultural  Chemistry. 
Elwood  Mead,  Rural  Institutions. 
H.  J.  Quayle,  Entomology. 
J.  B.  Davidson,  Agricultural  Engineering. 
H.  S.  Reed,  Plant  Physiology. 
D.  T.  Mason,  Forestry. 

William  G.  Hummel,  Agricultural  Education. 
Leon  M.  Davis,  Dairy  Industry. 
John  E.  Dougherty,  Poultry  Husbandry. 
S.  S.  Rogers,  Olericulture. 
*Frank  Adams,  Experimental  Irrigation. 
David  N.  Morgan,  Assistant  to  the  Director. 
Mrs.  D.  L.  Bunnell,  Librarian. 


*  Tn  co-operation  Office  of  Public  Roads  and  Rural  Engineering,  U.  S.  D.  A. 

CITRUS  EXPERIMENT   STATION 
DIVISION   OF    PLANT   PATHOLOGY 

J.  T.  Barrett  H.  S.  Fawcett 

C.  O.  Smith 


A  SPOTTING  OF  CITRUS  FRUITS  DUE  TO  THE  ACTION 
OF  OIL  LIBERATED  FROM  THE  RIND* 

By  HOWARD  S.  FAWCETT 


Among  the  various  spots  and  blemishes  of  lemons  and  oranges 
due  to  many  different  causes,  there  is  one  that  is  characterized  by  a 
slight  sinking  of  the  tissue  between  the  oil  glands  in  the  rind  leaving 
them  standing  out  prominently  over  the  surface  of  the  affected  areas. 
These  spots  vary  greatly  in  size  and  shape.  They  are  usually  circular 
in  outline  and  ordinarily  do  not  exceed  one-half  an  inch  in  diameter. 
They  may,  however,  be  irregular  in  outline  and  at  times  involve  the 
greater  portion  of  the  surface  of  a  fruit.  At  least  one  of  the  causes  of 
such  spotting  has  been  found  by  Mr.  J.  D.  Culbertson  and  the  writer  to 
be  due  to  the  remarkable  and  unexpected  effect  of  small  quantities 
of  oil  liberated  from  the  glands  in  the  rind.  The  oil  liberated  from 
the  rind  by  any  cause  appears  to  act  powerfully  and  quickly  upon 
all  the  cells  at  the  surface  with  which  it  comes  in  contact,  except 
those  immediately  surrounding  the  oil  glands.  This  leaves  the  oil 
glands  standing  out  prominently  over  the  surface  of  the  area  occupied 
by  the  spot.     (Figs.  1  and  2.) 

OCCURRENCE    AND    LOSSES 

The  greatest  trouble  from  this  spotting  appears  to  occur  in  the 
lemon  packing  houses,  especially  in  moist  cool  weather,  during  the  rainy 
season.  At  that  time,  severe  losses  are  often  experienced  by  what  is 
known  as  the  "green  spot."  The  lemons  which  come  to  standard 
size  while  green  appear  normal  when  picked,  but  on  being  set  aside 
to  cure  develop  spots  which  remain  green  while  the  remainder  of 
the  rind  colors  normally.  (Fig.  2.)  Such  fruits  may  be  kept  for 
weeks  without  enlargement  of  the  spots  and  without  change  in  their 
green  color.  Sometimes  the  green  is  replaced  after  a  long  time  by  a 
reddish  or  brownish  color,  but  the  normal  color  does  not  develop  in  the 
spots.  This  lowers  the  grade  of  the  fruit,  but  usually  does  not  injure 
seriously  its  keeping  quality.  Lemons  that  have  already  colored  before 
they  are  picked,  may  in  some  cases  show  spots  of  the  same  kind,  though 
not  green  and  therefore  less  conspicuous. 


*  Paper  No  23,  Citrus  Experiment  Station,  College  of  Agriculture,  Univer- 
sity of  California,  Riverside,  California. 

[261] 


262 


UNIVERSITY    OF    CALIFORNIA EXPERIMENT    STATION 


Fig.  1. — Immature  oranges  picked  in  November,  showing  the  manner  in  which 
the  cells  between  the  oil  glands  are  broken  down,  leaving  the  oil  glands  stand- 
ing out  prominently  over  the  surface  of  the  green  spots. 

(Photographed  by  J.  T.  Barrett.) 


SPOTTING    OF   CITRUS    FRUITS  263 

Oranges  picked  too  early  or  when  they  are  immature  may  also 
be  severely  affected  by  the  "green  spot."  (Fig.  1.)  Whether  or  not 
the  so-called  "brown  spot"  that  has  caused  much  trouble  in  past 
years  during  the  winter  months,  is  due  in  part  to  this  cause  has  not 
been  determined. 


EXPERIMENTS  AND  OBSERVATIONS  LEADING  TO  THE  CAUSE 

The  experiments  of  Mr.  J.  D.  Culbertson  of  the  Limoneira  Com- 
pany, Santa  Paula,  California,  led  to  the  discovery  of  at  least  one 
cause  of  this  green  spotting.  More  than  a  year  ago  he  produced  what 
appeared  to  be  typical  green  spotting  on  lemons  by  pressing  and  roll- 
ing them  against  boards.  After  putting  them  away  for  some  weeks, 
apparently  tvpical  green  spots  developed.  At  that  time  the  spotting 
was  thought  to  be  due  to  the  injury  to  the  cells  themselves  rather  than 
to  the  oil.  It  was  also  noticed  at  that  time  that  fruit  picked  from 
branches  that  had  been  cut  off  in  pruning  and  were  lying  on  the 
ground  developed  more  green  spotting  than  others  picked  directly 
from  the  trees.  Other  lemon  growers  had  noticed  that  fruit  picked 
when  dark  green  and  wet  usually  developed  more  "green  spot"  than 
similar  fruit  picked  dry  from  the  same  trees.  Mr.  Culbertson  states 
that  in  washing  a  lot  of  lemons  picked  late  in  November,  1914,  while 
still  wet  with  an  early  morning  shower,  a  strong  smell  of  lemon  oil 
was  detected  by  the  men  at  the  washer  as  the  fruit  came  through  the 
washing  machine  and  that  inspection  of  these  lemons  later  showed 
them  to  be  severely  injured  from  green  spotting.  This  led  them  to 
suspect  that  lemon  oil  itself  might  be  responsible  for  the  trouble,  and 
early  in  December,  just  after  a  shower,  Mr.  Culbertson  injured  some 
lemons  hanging  on  the  tree  so  that  the  oil  ran  out  over  the  uninjured 
surface,  and  also  placed  some  of  this  oil  on  the  uninjured  surface  of 
other  fruits.  The  sinking  of  the  tissue  as  in  the  green  spot  took  place, 
but  the  green  color  did  not  appear  as  it  did  on  the  stored  fruit.  It 
was  later  found  in  our  experiments  that  the  green  color  rarely  re- 
mained on  spots  injured  by  lemon  oil  if  the  fruit  were  left  on  the  tree, 
but  that  if  it  were  picked  and  stored  the  green  color  usually  remained 
fixed. 

Dr.  J.  T.  Barrett,  in  making  observations  in  Tulare  County  in 
December,  1913,  noticed  on  the  trees  many  fully  colored  oranges  with 
spots  that  probably  had  been  typical  green  spots  (or  would  have  been 
had  they  been  picked  earlier),  that  by  remaining  on  the  tree  had 
assumed  almost  the  normal  color  of  the  fully  colored  rind. 


264  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT    STATION 


Fig.  2. — Cured  lemons  in  November,  showing  the  same  type  of  spots  as  in 
figure  1.  The  darker  areas  indicate  the  green  spots  that  have  developed  in  the 
usual  process  of  curing. 

(Photographed  by  C.  O.  Smith.) 


SPOTTING    OF    CITRUS    FRUITS  265 


FURTHER    EXPERIMENTS    WITH    LEMON    AND    ORANGE    OIL 

In  an  experiment  by  the  writer,  begun  in  February,  1915,  the 
typical  green  spots  were  developed  by  very  small  amounts  of  lemon 
oil  acting  on  the  uninjured  surface  of  green  lemons  in  moist  jars. 
Twelve  lemons  were  picked  very  carefully  to  avoid  any  injuries  on 
February  17,  1915,  while  they  were  still  wet  from  a  rain.  Three  lots 
of  four  each  were  placed  in  moist  jars.  On  the  uninjured  upper 
surface  of  the  first  lot,  a  small  amount  of  oil  from  a  portion  of  the 
peel  of  another  green  fruit  was  squeezed  out  by  hand.  A  small  area 
on  the  rind  of  each  of  the  second  lot  was  pressed  with  the  blunt  end 
of  the  flat  handle  of  a  scalpel  until  oil  was  seen  to  appear  on  the 
surface.  The  third  lot  was  left  untreated  as  checks.  The  jars  were 
kept  covered  to  retain  the  moisture.  On  March  18,  1915,  all  the  fruits 
in  the  first  lot  on  which  the  lemon  oil  had  remained  on  the  uninjured 
surface  showed  typical  spots  where  the  oil  had  broken  down  the  tissue 
between  the  oil  glands.  On  two,  the  spots  were  green  and  on  the 
others,  they  were  reddish  to  brownish.  The  portion  of  the  surface 
unspotted  was  coloring  in  the  normal  way.  The  second  lot  of  fruits 
which  had  been  pressed  with  the  end  of  a  scalpel,  showed  the  same 
kind  of  spots.  The  spots  were  larger  that  the  actual  area  pressed  by 
the  scalpel  handle  due  to  the  spreading  of  the  oil  over  the  uninjured 
surface  beyond  the  bruised  spot.  On  the  third  lot  kept  as  checks  no 
spotting  occurred. 

Another  experiment  with  lemons  to  compare  the  effect  of  lemon 
oil  on  dry  and  moist  fruits  was  begun  March  4,  1915.  Four  jars 
with  four  fruits  each  were  prepared.  For  the  first,  the  green  fruits 
freshly  picked  from  the  trees  were  put  in  dry  without  washing  and 
the  lemon  oil  squeezed  on  a  portion  of  their  uninjured  surfaces  and 
the  jar  left  open.  For  the  second,  the  fruit  was  first  washed  and 
placed  in  the  jar  wet  and  the  lemon  oil  squeezed  on  as  in  the  first 
and  the  jar  covered.  The  third  and  fourth  jars  were  for  checks,  the 
fruit  for  one  being  put  in  dry  and  the  jar  left  open,  and  the  fruit 
for  the  other  being  washed  and  the  jar  covered.  Three  out  of  four 
of  the  first  lot  kept  dry  showed  spots  on  March  18th,  only  one  of 
which  was  green.  All  in  the  second  lot  kept  wet,  showed  typical  spots 
while  none  of  the  fruits  on  which  no  lemon  oil  was  squeezed  in  the 
two  check  jars  showed  any  spots. 

Besides  experiments  with  oil  squeezed  directly  from  the  living 
rind  of  other  fruit,  experiments  were  also  tried  with  measured  quan- 


266  UNIVERSITY   OF    CALIFORNIA EXPERIMENT    STATION 

tities  of  commercially  expressed  lemon  oil.*  This  lemon  oil  acted  on 
the  rind  in  the  same  manner  as  the  oil  squeezed  directly  from  the 
living  rind. 

In  conducting  experiments  with  lemon  oil,  it  was  observed  that 
the  action  of  the  oil  in  breaking  down  the  tissue  was  very  rapid.  In 
order  to  find  out  something  as  to  the  length  of  time  necessary  for 
the  oil  to  produce  visible  injury,  the  following  experiment  was  tried : 

Nineteen  full-sized  light  green  lemons  were  placed  in  a  row  on 
the  table  in  the  laboratory  and  drops  containing  one  one-hundreth 
(0.01)  of  a  cubic  centimeter  were  dropped  on  each.  The  drop  on  the 
first  was  rubbed  off  immediately  with  a  piece  of  cotton.  The  other 
drops  were  rubbed  off  after  they  had  remained  on  the  rind  different 
periods ;  namely,  3,  6,  7,  8,  9,  10,  15,  20,  30,  and  45  seconds ;  1,  2,  5, 
10,  20,  and  30  minutes ;  1  and  2  hours,  respectively.  A  visible  effect 
of  the  oil  was  seen  in  a  very  short  time  on  those  left  on  two  or  more 
minutes.  On  the  one  on  which  the  oil  had  acted  2  minutes  a  slight 
effect  was  visible  in  20  minutes  after  the  oil  was  rubbed  off,  and  on 
the  one  on  which  the  oil  had  acted  5  minutes,  the  effect  was  visible 
in  10  minutes  after  the  oil  was  rubbed  off.  In  24  hours  the  fruit  on 
which  the  oil  had  acted  for  approximately  8  seconds,  showed  a  slight 
effect.  On  all  those  on  which  the  oil  had  acted  less  than  8  seconds, 
no  effect  was  visible,  even  after  several  weeks.  The  severity  of  effect 
was  in  proportion  to  the  length  of  time  the  oil  had  acted  upon  the  rind 
with  slight  variations,  probably  due  to  differences  in  the  fruit.  The 
experiment  showed  clearly  that  the  action  of  the  oil  in  breaking  down 
the  surface  cells  is  extremely  rapid. 

During  the  months  of  March  and  April,  a  large  number  of  different 
experiments  were  carried  out  by  putting  different  quantities  of  lemon 
and  orange  oil  from  the  rind  on  more  than  150  fruits  of  all  ages  of 
both  lemons  and  oranges.  The  effect  of  the  oil  was  further  compared 
in  both  moist  and  dry  atmosphere  on  fruit  both  on  and  off  the  tree. 
The  effect  of  the  oil  was  also  tested  on  young  shoots,  leaves  and  flower 
buds.  The  following  is  a  summary  of  the  results  of  the  various  ex- 
periments : 

1.  The  effect  of  a  given  amount  of  oil  from  the  rind  was  greater 
on  fruit  in  a  moist  atmosphere  than  on  similar  fruit  in  a  dry  atmos- 
phere. 

2.  The  moisture  being  the  same,  the  effect  was  greater  on  green 
or  immature  fruit  than  on  fully  colored  or  mature  fruit. 


*  I  am  indebted  to  Mr.  C.  P.  Wilson,  of  the  Citrus  By-Products  Laboratory 
of  the  Bureau  of  Chemistry,  United  States  Department  of  Agriculture,  Los 
Angeles,  California,    for  two  samples  of  lemon  oil  for  use  in  the  experiments. 


spotting  of  errors  fruits  267 

3.  The  effect  was  greater  on  fruit  just  picked  than  on  similar 
fruit  picked  for  some  days. 

4.  The  action  of  small  amounts  of  oil,  for  example,  such  as  could 
be  liberated  by  a  hard  pressure  of  the  thumb  against  the  rind  of  a 
dark  green  freshly  picked  moist  lemon  (or  by  .01  cc.  of  the  com- 
mercially expressed  lemon  oil),  was  sufficient  to  cause  the  typical  green 
spotting.  The  green  color  appeared  to  be  fixed  in  the  portion  acted 
on  by  the  oil  while  the  remainder  of  the  rind  colored  normally  in  the 
usual  process  of  curing  in  four  to  six  weeks. 

5.  The  action  of  a  large  amount  of  lemon  oil,  such  as  one-tenth 
of  a  cubic  centimeter  or  more,  under  the  same  conditions  caused  the 
spots  to'  become  brownish  or  reddish  rather  than  green.  When  the 
amount  was  sufficiently  increased  the  breaking  down  of  the  tissue  was 
so  great  that  blue  mold  started  in  a  few  days. 

6.  When  the  fruits  acted  on  by  the  oil  were  left  attached  to  the 
tree,  only  in  rare  cases  did  the  green  color  remain.  As  the  fruits 
continued  to  grow  and  mature,  the  sunken  areas  were  partially  restored 
and  only  slight  scars  were  left. 

7.  Under  similar  conditions  the  oil  from  the  rind  of  oranges  acted 
upon  other  uninjured  oranges  in  the  same  manner  as  did  the  oil  from 
the  rind  of  lemons  act  upon  other  lemons. 

8.  The  oil  caused  the  spotting  of  tender  leaves  and  shoots  and 
the  withering  of  flower  buds  when  squeezed  out  upon  them. 

9.  The  action  of  the  oil  on  the  surface  of  the  rind  is  extremely 
rapid,  as  shown  by  the  fact  that  one  one-hundreth  of  a  cubic  centi- 
meter of  lemon  oil  acting  for  eight  seconds  was  sufficient  to  show 
afterward  a  visible  effect  on  the  rind. 

The  results  of  these  experiments  aid  us  in  explaining  some  of  the 
following  observed  facts  in  connection  with  the  occurrence  of  the  so- 
called  green  spot. 

Green  spotting  has  been  observed  almost  exclusively  on  fruit  picked 
during  the  late  fall,  winter  and  early  spring.  This  in  general  corres- 
ponds to  the  season  of  moist  atmospheric  conditions  in  California  due  to 
frequent  rains  and  fogs.  It  has  also  been  observed,  as  stated  before, 
that  fruit  picked  while  wet  after  a  rain  is  more  apt  to  spot  than  that 
picked  dry.  The  experiments  have  shown  that  the  same  quantities  of 
oil,  other  things  being  equal,  has  more  effect  in  a  moist  than  in  a 
dry  atmosphere,  on  wet  than  on  dry  fruit.  The  lemons  picked  at 
the  above  mentioned  season  are  apt  to  contain  a  higher  percentage  of 
dark  green  fruit  that  at  other  seasons.  The  experiments  have  also 
shown  that  the  oil  had  more  effect  on  green  than  on  ripe  fruit.  The 
explanation  would  therefore  appear  to  be  this;  that  in  the  process  of 


268  UNIVERSITY   OF    CALIFORNIA — EXPERIMENT   STATION 

picking  and  handling,  certain  small  amounts  of  oil  are  liberated  on 
the  surface  of  the  rind,  and  that  this  oil  is  able  to  cause  severe  spotting 
in  a  moist  atmosphere  or  when  the  fruit  is  wet,  as  is  often  the  case 
during  the  rainy  season,  especially  when  it  is  green.  That  no  serious 
trouble  from  green  spotting  is  experienced  in  summer  is  probably 
due  to  the  dryer  atmosphere  and  the  greater  maturity  of  the  fruit. 
In  a  dry  atmosphere  the  oil  would  quickly  volatilize  and  therefore 
have  little  time  to  act. 

Then  there  occur  spots  on  fruit  on  the  tree  in  connection  with 
scratches  or  bruises  from  passing  teams  that  in  size  appear  to  be  out 
of  all  proportion  to  the  mechanical  injury  inflicted.  In  many  cases 
an  area  may  be  traced  where  the  oil  has  spread  out  from  the  broken 
cells  affecting  the  adjacent  tissue  in  the  same  manner  as  in  the  spotting 
under  consideration.  It  also  seems  probable  that  in  like  manner  the 
injury  following  red  spider,  and  other  mites  and  insects  is  emphasized 
by  the  liberation  of  oil.  The  injuries  due  to  the  whipping  of  the  fruit 
against  the  branches  by  the  wind  in  severe  storms  are  also  probably 
more  severe  for  the  same  reason. 

It  has  also  been  observed  by  packing-house  men  that  there  is  great 
variation  in  the  spotting  between  fruit  from  various  groves  handled 
under  the  same  conditions.  This  may  be  due  in  part  to  variations  in 
maturity  or  growth  conditions  of  the  fruit  that  might  modify  the 
structure  of  the  rind  and  possibly  the  amount  of  oil  in  it.  The  oil  is 
probably  liberated  much  more  easily  from  fruits  from  certain  groves 
than  others,  due  possibly  to  these  differences  in  the  fruit  itself. 


EEMEDIES 

One  very  obvious  remedy  is  to  avoid  picking  fruit  when  wet  either 
with  rain  or  dew.  That  this  has  proved  to  be  a  practical  remedy  in 
some  cases  is  shown  by  the  following  examples. 

Mr.  Culbertson  of  the  Limoneira  Company,  Santa  Paula,  writes : 
"Since  the  first  of  December  we  have  carefully  avoided  picking  lemons 
too  soon  after  a  rain  or  extra  heavy  dew,  until  it  developed  that  we 
were  getting  practically  no  green  spot.  The  disappearance  of  the  spot 
later  was  probably  due  also  to  the  greater  maturity  of  the  lemons." 

Mr.  M.  Perry  of  the  Teague  McKevitt  Ranch,  showed  the  writer 
two  sets  of  lemons,  one  set  picked  in  the  early  morning  after  a  rain, 
the  other  picked  from  the  same  trees  and  by  the  same  pickers  near  the 
middle  of  the  same  day  when  the  fruit  was  dry.     The  first  lot  picked 


SPOTTING   OF    CITRUS   FRUITS  269 

wet   was   badly   spotted;    the    second,    picked    dry,    showed   only    an 
occasional  spot. 

Another  remedy  that  suggests  itself,  is  extreme  care  in  handling 
the  fruit  to  avoid  injuries  or  knocks  that  would  tend  to  liberate  the 
oil  in  the  rind.  It  has  been  recognized  for  a  long  time  that  great  care 
in  handling  the  fruit  is  necessary  in  avoiding  decay  from  blue  mold. 
To  avoid  green  spotting  on  susceptible  fruit  during  the  critical  season 
even  greater  care  will  doubtless  be  necessary.  Pressing  together  of  the 
fruit  in  the  picking  sacks,  letting  them  drop  too  far  into  the  field 
boxes,  jolting  in  wagons  without  springs  on  rough  roads,  rough  knocks 
and  jamming  in  washing,  grading  and  packing  are  all  means  that 
would  tend  to  liberate  the  oil  from  the  rind. 


STATION  PUBLICATIONS  AVAILABLE  FOR  DISTRIBUTION 


REPORTS 

1897.      Resistant  Vines,  their  Selection,  Adaptation,  and  Grafting.     Appendix  to  Viticultural 
Report  for  1896. 

1902.  Report  of  the  Agricultural  Experiment  Station  for   1898-1901. 

1903.  Report  of  the  Agricultural  Experiment  Station  for   1901-03. 

1904       Twenty-second  Report  of  the  Agricultural  Experiment  Station  for  1903-04. 

1914.  Report  of  the  College  of  Agriculture  and  the  Agricultural  Experiment   Station,   July, 

1913-June,   1914.  . 

1915.  Report  of  the  College  of  Agriculture  and  the  Agricultural  Experiment   Station,   July, 

1914-June,   1915. 


No. 
168. 

169. 
174. 

178. 
184. 

185. 

195. 
197. 


198. 
203. 

207. 
208. 
212. 
213. 
216. 


220. 
225. 

227. 
230. 


BULLETINS 
No. 


Observations  on  Some  Vine  Diseases 
in   Sonoma  County. 

Tolerance  of  the  Sugar  Beet  for  Alkali. 

A  New  Wine-Cooling  Machine. 

Mosquito  Control. 

Report  of  the  Plant  Pathologist  to 
July   1,    1906. 

Report  of  Progress  in  Cereal  Investi- 
gations. 

The  California   Grape  Root-worm. 

Grape  Culture  in  California ;  Improved 
Methods  of  Wine-making ;  Yeast  from 
California  Grapes. 

The   Grape  Leaf-Hopper. 

Report  of  the  Plant  Pathologist  to 
Julv   1,    1909. 

The  Control  of  the  Argentine  Ant. 

The  Late  Blight  of  Celery. 

California  White  Wheats. 

The   Principles  of  Wine-making. 

A  Progress  Report  Upon  Soil  and  Cli- 
matic Factors  Influencing  the  Com- 
position of  Wheat. 

Dosage  Tables. 

Tolerance  of  Eucalyptus  for  Alkali. 

Grape  Vinegar. 

Enological  Investigations. 


234. 
241. 
242. 
244. 
246. 
248. 

249. 
250. 
251. 


zoz. 

253. 

254. 
255. 
256. 

257. 
258. 
261. 

262. 

263. 

264. 


Red  Spiders  and  Mites  of  Citrus  Trees. 
Vine  Pruning  in  California,  Part  I. 
Humus   in  California  Soils. 
Utilization  of  Waste  Oranges. 
Vine   Pruning  in   California,    Part  II. 
The  Economic  Value  of  Pacific  Coast 

Kelps. 
Stock-Poisoning  Plants  of  California. 
The  Loquat. 
Utilization  of  the  Nitrogen  and  Organic 

Matter   in    Septic   and    Imhoff   Tank 

Sludges. 
Deterioration  of  Lumber. 
Irrigation   and   Soil  Conditions   in  the 

Sierra   Nevada   Foothills,    California. 
The  Avocado  in  California. 
The  Citricola  Scale. 
Value  of  Barley  for  Cows  Fed  Alfalfa. 
New  Dosage  Tables. 
Mealv  Bugs  of  Citrus  Trees. 
Melaxuma    of    the    Walnut,    "Juglans 

regia." 
Citrus   Diseases   of   Florida   and   Cuba 

Compared  with  Those  of  California. 
Size  Grade  for  Ripe  Olives. 
The  Calibration  of  the  Leakage  Meter. 


No.  .  .,     , 

65.   The  California   Insecticide  Law. 

69.  The    Extermination    of    Morning-Glory. 

70.  Observations    on    the    Status    of    Corn 

Growing   in   California. 
76.   Hot  Room   Callusing. 
80.   Boys'   and  Girls'   Clubs. 

82.  The     Common     Ground     Squirrels     of 

California. 

83.  Potato  Growing  Clubs. 

100.   Pruning  Frosted  Citrus   Trees. 

106.  Directions  for  Using  Anti-Hog  Cholera 

Serum.  . 

107.  Spraying  Walnut  Trees  for  Blight  and 

Aphis    Control. 

108.  Grape  Juice.  . 

109  Communitv  or  Local  Extension  Work 
by  the  High  School  Agricultural  De- 
partment. 

110.  Green  Manuring  in  California. 

111.  The  Use  of  Lime  and  Gypsum  on  Cali- 

fornia Soils.  . 

113.  Correspondence  Courses  in  Agriculture. 

114.  Increasing  the  Dutv  of  Water. 

115.  Grafting  Vinifera  Vineyards. 

117.  The    Selection    and    Cost    of    a    Small 

Pumping  Plant. 

118.  The  County  Farm  Bureau. 

119.  Winery  Directions.  . 

121.  Some    Things    the    Prospective    Settler 

Should  Know. 

122.  The  Management  of   Strawberry   Soils 

in  Pajaro  Valley. 


CIRCULARS 
No. 


124. 
125. 
126. 
127. 
128. 
129. 
130. 
131. 
132. 

133. 
134. 
135. 
136. 
137. 
138. 
139. 


140. 


141. 

142. 

143. 

144. 
145. 

146. 


Alfalfa   Silage  for  Fattening   Steers. 

Aphids  on  Grain  and  Cantaloupes. 

Spraying  for  the  Grape  Leaf  Hopper. 

House  Fumigation. 

Insecticide  Formulas. 

The  Control  of  Citrus  Insects. 

Cabbage   Growing  in   California. 

Spraving  for  Control  of  Walnut  Aphis. 

When  to  Vaccinate  against  Hog 
Cholera. 

County  Farm  Adviser. 

Control   of   Raisin   Insects. 

Official  Tests  of  Dairy  Cows. 

Melilotus   Indica. 

Wood  Decay  in  Orchard  Trees. 

The  Silo  in  California  Agriculture. 

The  Generation  of  Hydrocyanic  Acid 
Gas  in  Fumigation  by  Portable  Ma- 
chines. 

The  Practical  Application  of  Improved 
Methods  of  Fermentation  in  Califor- 
nia Wineries  during  1913  and  1914. 

Standard  Insecticides  and  Fungicides 
versus   Secret  Preparations. 

Practical  and  Inexpensive  Poultry  Ap- 
pliances. . 

Control  of  Grasshoppers  in  Imperial 
Valley. 

Oidium  or  Powdery  Mildew  of  the  Vine. 

Suggestions  to  Poultrymen  concerning 
Chicken  Pox. 

Jellies  and  Marmalades  from  Citrus 
Fruits. 


